| 1597 Role of the FGFR3-Mediated Signaling Pathway in Skeletogenesis of the Chick Mandibular Arch | ||
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D.A. VELONIS1, M.S. KRONENBERG2, B.L. OLIVER1, A.C. LICHTLER3, and M. MINA1, 1 University of Connecticut Health Center School of Dental Medicine, Farmington, USA, 2 University of Connecticut Health Center School of Medicine, Farmington, USA, 3 University of Connecticut Health Center, Farmington, USA Analysis of gain- and loss-of-function mutations in Fibroblast Growth Factor Receptor-3 (FGFR3) in humans and mice has provided direct evidence that signaling through FGFR3 is involved in limiting chondrocyte proliferation and maturation in the long bones. Our studies in the embryonic chick mandible showed expression of Fgfr3 in the condensing mesenchyme of Meckel's cartilage and developing bones. Later Fgfr3 was expressed in periosteum of mandibular bones and in differentiated Meckelian chondrocytes. Objective: To gain insight into functions of FGFR3-mediated signaling in mandibular osteogenesis and preventing maturation in chick Meckel's cartilage by blocking FGF/FGFR3-IIIc signaling. Methods: A dominant-negative Fgfr3 construct consisting of a kinase-deleted form of murine Fgfr3-IIIc cDNA bearing a c-myc epitope tag was generated and cloned into a replication-competent avian retroviral vector (RCAS-DN-mFgfr3). For Western blot analysis and immunocytochemistry chicken embryo fibroblasts (CEFs) were infected with RCAS-DN-mFgfr3. The stage-specific effects of blocking FGF/FGFR3-IIIc signaling on mandibular skeletogenesis were examined by injection of RCAS-DN-mFgfr3 into the right side of developing mandibles of chick embryos in vivo. Embryos were allowed to develop for 5-10 days after injection and processed for whole mount skeletal staining and histological analyses. Results: Western blot analysis showed expression of a major recombinant protein of approximately 78 kD in infected CEFs. Greater than 80% of CEFs stained positive for the c-myc epitope. Injection of RCAS-DN-mFgfr3, but not control virus (RCAS-GFP), at stages 17-22 resulted in various abnormalities in the developing mandibles on the treated side. The abnormalities included decreases in the length of mandibular processes and Meckel's cartilage, partial or complete absence of mandibular bones, and localized thickenings in Meckel's cartilage. Further experiments are in progress to analyze the underlying mechanisms leading to these defects. Conclusions: Our results provide evidence for involvement of FGFR3 signaling in skeletogenesis of the chick mandible. Supported by NIH grant DE08682. | ||
| Seq #201 - Senior Category 11:00 AM-12:15 PM, Saturday, 15 March 2003 Henry B. Gonzalez Convention Center Exhibit Hall C | ||
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